/*
 * Windows CE backend for libusb 1.0
 * Copyright © 2011-2013 RealVNC Ltd.
 * Large portions taken from Windows backend, which is
 * Copyright © 2009-2010 Pete Batard <pbatard@gmail.com>
 * With contributions from Michael Plante, Orin Eman et al.
 * Parts of this code adapted from libusb-win32-v1 by Stephan Meyer
 * Major code testing contribution by Xiaofan Chen
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <libusbi.h>

#include <stdint.h>
#include <errno.h>
#include <inttypes.h>

#include "wince_usb.h"

// Forward declares
static int wince_clock_gettime(int clk_id, struct timespec *tp);
unsigned __stdcall wince_clock_gettime_threaded(void* param);

// Global variables
uint64_t hires_frequency, hires_ticks_to_ps;
int errno;
const uint64_t epoch_time = UINT64_C(116444736000000000);       // 1970.01.01 00:00:000 in MS Filetime
enum windows_version windows_version = WINDOWS_CE;
static int concurrent_usage = -1;
// Timer thread
// NB: index 0 is for monotonic and 1 is for the thread exit event
HANDLE timer_thread = NULL;
HANDLE timer_mutex = NULL;
struct timespec timer_tp;
volatile LONG request_count[2] = {0, 1};    // last one must be > 0
HANDLE timer_request[2] = { NULL, NULL };
HANDLE timer_response = NULL;
HANDLE driver_handle = INVALID_HANDLE_VALUE;

/*
 * Converts a windows error to human readable string
 * uses retval as errorcode, or, if 0, use GetLastError()
 */
#if defined(ENABLE_LOGGING)
static char* windows_error_str(uint32_t retval)
{
    static TCHAR wErr_string[ERR_BUFFER_SIZE];
    static char err_string[ERR_BUFFER_SIZE];

    DWORD size;
    size_t i;
    uint32_t error_code, format_error;

    error_code = retval?retval:GetLastError();

    safe_stprintf(wErr_string, ERR_BUFFER_SIZE, _T("[%d] "), error_code);

    size = FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM, NULL, error_code,
        MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), &wErr_string[safe_tcslen(wErr_string)],
        ERR_BUFFER_SIZE - (DWORD)safe_tcslen(wErr_string), NULL);
    if (size == 0) {
        format_error = GetLastError();
        if (format_error)
            safe_stprintf(wErr_string, ERR_BUFFER_SIZE,
                _T("Windows error code %u (FormatMessage error code %u)"), error_code, format_error);
        else
            safe_stprintf(wErr_string, ERR_BUFFER_SIZE, _T("Unknown error code %u"), error_code);
    } else {
        // Remove CR/LF terminators
        for (i=safe_tcslen(wErr_string)-1; ((wErr_string[i]==0x0A) || (wErr_string[i]==0x0D)); i--) {
            wErr_string[i] = 0;
        }
    }
    if (WideCharToMultiByte(CP_ACP, 0, wErr_string, -1, err_string, ERR_BUFFER_SIZE, NULL, NULL) < 0)
    {
        strcpy(err_string, "Unable to convert error string");
    }
    return err_string;
}
#endif

static struct wince_device_priv *_device_priv(struct libusb_device *dev)
{
        return (struct wince_device_priv *) dev->os_priv;
}

// ceusbkwrapper to libusb error code mapping
static int translate_driver_error(int error)
{
    switch (error) {
        case ERROR_INVALID_PARAMETER:
            return LIBUSB_ERROR_INVALID_PARAM;
        case ERROR_CALL_NOT_IMPLEMENTED:
        case ERROR_NOT_SUPPORTED:
            return LIBUSB_ERROR_NOT_SUPPORTED;
        case ERROR_NOT_ENOUGH_MEMORY:
            return LIBUSB_ERROR_NO_MEM;
        case ERROR_INVALID_HANDLE:
            return LIBUSB_ERROR_NO_DEVICE;
        case ERROR_BUSY:
            return LIBUSB_ERROR_BUSY;

        // Error codes that are either unexpected, or have
        // no suitable LIBUSB_ERROR equivilant.
        case ERROR_CANCELLED:
        case ERROR_INTERNAL_ERROR:
        default:
            return LIBUSB_ERROR_OTHER;
    }
}

static int init_dllimports()
{
    DLL_LOAD(ceusbkwrapper.dll, UkwOpenDriver, TRUE);
    DLL_LOAD(ceusbkwrapper.dll, UkwGetDeviceList, TRUE);
    DLL_LOAD(ceusbkwrapper.dll, UkwReleaseDeviceList, TRUE);
    DLL_LOAD(ceusbkwrapper.dll, UkwGetDeviceAddress, TRUE);
    DLL_LOAD(ceusbkwrapper.dll, UkwGetDeviceDescriptor, TRUE);
    DLL_LOAD(ceusbkwrapper.dll, UkwGetConfigDescriptor, TRUE);
    DLL_LOAD(ceusbkwrapper.dll, UkwCloseDriver, TRUE);
    DLL_LOAD(ceusbkwrapper.dll, UkwCancelTransfer, TRUE);
    DLL_LOAD(ceusbkwrapper.dll, UkwIssueControlTransfer, TRUE);
    DLL_LOAD(ceusbkwrapper.dll, UkwClaimInterface, TRUE);
    DLL_LOAD(ceusbkwrapper.dll, UkwReleaseInterface, TRUE);
    DLL_LOAD(ceusbkwrapper.dll, UkwSetInterfaceAlternateSetting, TRUE);
    DLL_LOAD(ceusbkwrapper.dll, UkwClearHaltHost, TRUE);
    DLL_LOAD(ceusbkwrapper.dll, UkwClearHaltDevice, TRUE);
    DLL_LOAD(ceusbkwrapper.dll, UkwGetConfig, TRUE);
    DLL_LOAD(ceusbkwrapper.dll, UkwSetConfig, TRUE);
    DLL_LOAD(ceusbkwrapper.dll, UkwResetDevice, TRUE);
    DLL_LOAD(ceusbkwrapper.dll, UkwKernelDriverActive, TRUE);
    DLL_LOAD(ceusbkwrapper.dll, UkwAttachKernelDriver, TRUE);
    DLL_LOAD(ceusbkwrapper.dll, UkwDetachKernelDriver, TRUE);
    DLL_LOAD(ceusbkwrapper.dll, UkwIssueBulkTransfer, TRUE);
    DLL_LOAD(ceusbkwrapper.dll, UkwIsPipeHalted, TRUE);
    return LIBUSB_SUCCESS;
}

static int init_device(struct libusb_device *dev, UKW_DEVICE drv_dev,
                       unsigned char bus_addr, unsigned char dev_addr)
{
    struct wince_device_priv *priv = _device_priv(dev);
    int r = LIBUSB_SUCCESS;

    dev->bus_number = bus_addr;
    dev->device_address = dev_addr;
    priv->dev = drv_dev;

    if (!UkwGetDeviceDescriptor(priv->dev, &(priv->desc))) {
        r = translate_driver_error(GetLastError());
    }
    return r;
}

// Internal API functions
static int wince_init(struct libusb_context *ctx)
{
    int i, r = LIBUSB_ERROR_OTHER;
    HANDLE semaphore;
    TCHAR sem_name[11+1+8]; // strlen(libusb_init)+'\0'+(32-bit hex PID)

    _stprintf(sem_name, _T("libusb_init%08X"), (unsigned int)GetCurrentProcessId()&0xFFFFFFFF);
    semaphore = CreateSemaphore(NULL, 1, 1, sem_name);
    if (semaphore == NULL) {
        usbi_err(ctx, "could not create semaphore: %s", windows_error_str(0));
        return LIBUSB_ERROR_NO_MEM;
    }

    // A successful wait brings our semaphore count to 0 (unsignaled)
    // => any concurent wait stalls until the semaphore's release
    if (WaitForSingleObject(semaphore, INFINITE) != WAIT_OBJECT_0) {
        usbi_err(ctx, "failure to access semaphore: %s", windows_error_str(0));
        CloseHandle(semaphore);
        return LIBUSB_ERROR_NO_MEM;
    }

    // NB: concurrent usage supposes that init calls are equally balanced with
    // exit calls. If init is called more than exit, we will not exit properly
    if ( ++concurrent_usage == 0 ) {    // First init?
        // Initialize pollable file descriptors
        init_polling();

        // Load DLL imports
        if (init_dllimports() != LIBUSB_SUCCESS) {
            usbi_err(ctx, "could not resolve DLL functions");
            r = LIBUSB_ERROR_NOT_SUPPORTED;
            goto init_exit;
        }

        // try to open a handle to the driver
        driver_handle = UkwOpenDriver();
        if (driver_handle == INVALID_HANDLE_VALUE) {
            usbi_err(ctx, "could not connect to driver");
            r = LIBUSB_ERROR_NOT_SUPPORTED;
            goto init_exit;
        }

        // Windows CE doesn't have a way of specifying thread affinity, so this code
        // just has  to hope QueryPerformanceCounter doesn't report different values when
        // running on different cores.
        r = LIBUSB_ERROR_NO_MEM;
        for (i = 0; i < 2; i++) {
            timer_request[i] = CreateEvent(NULL, TRUE, FALSE, NULL);
            if (timer_request[i] == NULL) {
                usbi_err(ctx, "could not create timer request event %d - aborting", i);
                goto init_exit;
            }
        }
        timer_response = CreateSemaphore(NULL, 0, MAX_TIMER_SEMAPHORES, NULL);
        if (timer_response == NULL) {
            usbi_err(ctx, "could not create timer response semaphore - aborting");
            goto init_exit;
        }
        timer_mutex = CreateMutex(NULL, FALSE, NULL);
        if (timer_mutex == NULL) {
            usbi_err(ctx, "could not create timer mutex - aborting");
            goto init_exit;
        }
        timer_thread = CreateThread(NULL, 0, wince_clock_gettime_threaded, NULL, 0, NULL);
        if (timer_thread == NULL) {
            usbi_err(ctx, "Unable to create timer thread - aborting");
            goto init_exit;
        }

        // Wait for timer thread to init before continuing.
        if (WaitForSingleObject(timer_response, INFINITE) != WAIT_OBJECT_0) {
            usbi_err(ctx, "Failed to wait for timer thread to become ready - aborting");
            goto init_exit;
        }
    }
    // At this stage, either we went through full init successfully, or didn't need to
    r = LIBUSB_SUCCESS;

init_exit: // Holds semaphore here.
    if (!concurrent_usage && r != LIBUSB_SUCCESS) { // First init failed?
        if (driver_handle != INVALID_HANDLE_VALUE) {
            UkwCloseDriver(driver_handle);
            driver_handle = INVALID_HANDLE_VALUE;
        }
        if (timer_thread) {
            SetEvent(timer_request[1]); // actually the signal to quit the thread.
            if (WAIT_OBJECT_0 != WaitForSingleObject(timer_thread, INFINITE)) {
                usbi_warn(ctx, "could not wait for timer thread to quit");
                TerminateThread(timer_thread, 1); // shouldn't happen, but we're destroying
                                                  // all objects it might have held anyway.
            }
            CloseHandle(timer_thread);
            timer_thread = NULL;
        }
        for (i = 0; i < 2; i++) {
            if (timer_request[i]) {
                CloseHandle(timer_request[i]);
                timer_request[i] = NULL;
            }
        }
        if (timer_response) {
            CloseHandle(timer_response);
            timer_response = NULL;
        }
        if (timer_mutex) {
            CloseHandle(timer_mutex);
            timer_mutex = NULL;
        }
    }

    if (r != LIBUSB_SUCCESS)
        --concurrent_usage; // Not expected to call libusb_exit if we failed.

    ReleaseSemaphore(semaphore, 1, NULL);    // increase count back to 1
    CloseHandle(semaphore);
    return r;
}

static void wince_exit(void)
{
    int i;
    HANDLE semaphore;
    TCHAR sem_name[11+1+8]; // strlen(libusb_init)+'\0'+(32-bit hex PID)

    _stprintf(sem_name, _T("libusb_init%08X"), (unsigned int)GetCurrentProcessId()&0xFFFFFFFF);
    semaphore = CreateSemaphore(NULL, 1, 1, sem_name);
    if (semaphore == NULL) {
        return;
    }

    // A successful wait brings our semaphore count to 0 (unsignaled)
    // => any concurent wait stalls until the semaphore release
    if (WaitForSingleObject(semaphore, INFINITE) != WAIT_OBJECT_0) {
        CloseHandle(semaphore);
        return;
    }

    // Only works if exits and inits are balanced exactly
    if (--concurrent_usage < 0) {    // Last exit
        exit_polling();

        if (timer_thread) {
            SetEvent(timer_request[1]); // actually the signal to quit the thread.
            if (WAIT_OBJECT_0 != WaitForSingleObject(timer_thread, INFINITE)) {
                usbi_dbg("could not wait for timer thread to quit");
                TerminateThread(timer_thread, 1);
            }
            CloseHandle(timer_thread);
            timer_thread = NULL;
        }
        for (i = 0; i < 2; i++) {
            if (timer_request[i]) {
                CloseHandle(timer_request[i]);
                timer_request[i] = NULL;
            }
        }
        if (timer_response) {
            CloseHandle(timer_response);
            timer_response = NULL;
        }
        if (timer_mutex) {
            CloseHandle(timer_mutex);
            timer_mutex = NULL;
        }
        if (driver_handle != INVALID_HANDLE_VALUE) {
            UkwCloseDriver(driver_handle);
            driver_handle = INVALID_HANDLE_VALUE;
        }
    }

    ReleaseSemaphore(semaphore, 1, NULL);    // increase count back to 1
    CloseHandle(semaphore);
}

static int wince_get_device_list(
    struct libusb_context *ctx,
    struct discovered_devs **discdevs)
{
    UKW_DEVICE devices[MAX_DEVICE_COUNT];
    struct discovered_devs * new_devices = *discdevs;
    DWORD count = 0, i;
    struct libusb_device *dev = NULL;
    unsigned char bus_addr, dev_addr;
    unsigned long session_id;
    BOOL success;
    DWORD release_list_offset = 0;
    int r = LIBUSB_SUCCESS;

    success = UkwGetDeviceList(driver_handle, devices, MAX_DEVICE_COUNT, &count);
    if (!success) {
        int libusbErr = translate_driver_error(GetLastError());
        usbi_err(ctx, "could not get devices: %s", windows_error_str(0));
        return libusbErr;
    }
    for(i = 0; i < count; ++i) {
        release_list_offset = i;
        success = UkwGetDeviceAddress(devices[i], &bus_addr, &dev_addr, &session_id);
        if (!success) {
            r = translate_driver_error(GetLastError());
            usbi_err(ctx, "could not get device address for %d: %s", i, windows_error_str(0));
            goto err_out;
        }
        dev = usbi_get_device_by_session_id(ctx, session_id);
        if (dev) {
            usbi_dbg("using existing device for %d/%d (session %ld)",
                    bus_addr, dev_addr, session_id);
            // Release just this element in the device list (as we already hold a
            // reference to it).
            UkwReleaseDeviceList(driver_handle, &devices[i], 1);
            release_list_offset++;
        } else {
            usbi_dbg("allocating new device for %d/%d (session %ld)",
                    bus_addr, dev_addr, session_id);
            dev = usbi_alloc_device(ctx, session_id);
            if (!dev) {
                r = LIBUSB_ERROR_NO_MEM;
                goto err_out;
            }
            r = init_device(dev, devices[i], bus_addr, dev_addr);
            if (r < 0)
                goto err_out;
            r = usbi_sanitize_device(dev);
            if (r < 0)
                goto err_out;
        }
        new_devices = discovered_devs_append(new_devices, dev);
        if (!discdevs) {
            r = LIBUSB_ERROR_NO_MEM;
            goto err_out;
        }
        safe_unref_device(dev);
    }
    *discdevs = new_devices;
    return r;
err_out:
    *discdevs = new_devices;
    safe_unref_device(dev);
    // Release the remainder of the unprocessed device list.
    // The devices added to new_devices already will still be passed up to libusb,
    // which can dispose of them at its leisure.
    UkwReleaseDeviceList(driver_handle, &devices[release_list_offset], count - release_list_offset);
    return r;
}

static int wince_open(struct libusb_device_handle *handle)
{
    // Nothing to do to open devices as a handle to it has
    // been retrieved by wince_get_device_list
    return LIBUSB_SUCCESS;
}

static void wince_close(struct libusb_device_handle *handle)
{
    // Nothing to do as wince_open does nothing.
}

static int wince_get_device_descriptor(
   struct libusb_device *device,
   unsigned char *buffer, int *host_endian)
{
    struct wince_device_priv *priv = _device_priv(device);

    *host_endian = 1;
    memcpy(buffer, &priv->desc, DEVICE_DESC_LENGTH);
    return LIBUSB_SUCCESS;
}

static int wince_get_active_config_descriptor(
    struct libusb_device *device,
    unsigned char *buffer, size_t len, int *host_endian)
{
    struct wince_device_priv *priv = _device_priv(device);
    DWORD actualSize = len;
    *host_endian = 0;
    if (!UkwGetConfigDescriptor(priv->dev, UKW_ACTIVE_CONFIGURATION, buffer, len, &actualSize)) {
        return translate_driver_error(GetLastError());
    }
    return actualSize;
}

static int wince_get_config_descriptor(
    struct libusb_device *device,
    uint8_t config_index,
    unsigned char *buffer, size_t len, int *host_endian)
{
    struct wince_device_priv *priv = _device_priv(device);
    DWORD actualSize = len;
    *host_endian = 0;
    if (!UkwGetConfigDescriptor(priv->dev, config_index, buffer, len, &actualSize)) {
        return translate_driver_error(GetLastError());
    }
    return actualSize;
}

static int wince_get_configuration(
   struct libusb_device_handle *handle,
   int *config)
{
    struct wince_device_priv *priv = _device_priv(handle->dev);
    UCHAR cv = 0;
    if (!UkwGetConfig(priv->dev, &cv)) {
        return translate_driver_error(GetLastError());
    }
    (*config) = cv;
    return LIBUSB_SUCCESS;
}

static int wince_set_configuration(
    struct libusb_device_handle *handle,
    int config)
{
    struct wince_device_priv *priv = _device_priv(handle->dev);
    // Setting configuration 0 places the device in Address state.
    // This should correspond to the "unconfigured state" required by
    // libusb when the specified configuration is -1.
    UCHAR cv = (config < 0) ? 0 : config;
    if (!UkwSetConfig(priv->dev, cv)) {
        return translate_driver_error(GetLastError());
    }
    return LIBUSB_SUCCESS;
}

static int wince_claim_interface(
    struct libusb_device_handle *handle,
    int interface_number)
{
    struct wince_device_priv *priv = _device_priv(handle->dev);
    if (!UkwClaimInterface(priv->dev, interface_number)) {
        return translate_driver_error(GetLastError());
    }
    return LIBUSB_SUCCESS;
}

static int wince_release_interface(
    struct libusb_device_handle *handle,
    int interface_number)
{
    struct wince_device_priv *priv = _device_priv(handle->dev);
    if (!UkwSetInterfaceAlternateSetting(priv->dev, interface_number, 0)) {
        return translate_driver_error(GetLastError());
    }
    if (!UkwReleaseInterface(priv->dev, interface_number)) {
        return translate_driver_error(GetLastError());
    }
    return LIBUSB_SUCCESS;
}

static int wince_set_interface_altsetting(
    struct libusb_device_handle *handle,
    int interface_number, int altsetting)
{
    struct wince_device_priv *priv = _device_priv(handle->dev);
    if (!UkwSetInterfaceAlternateSetting(priv->dev, interface_number, altsetting)) {
        return translate_driver_error(GetLastError());
    }
    return LIBUSB_SUCCESS;
}

static int wince_clear_halt(
    struct libusb_device_handle *handle,
    unsigned char endpoint)
{
    struct wince_device_priv *priv = _device_priv(handle->dev);
    if (!UkwClearHaltHost(priv->dev, endpoint)) {
        return translate_driver_error(GetLastError());
    }
    if (!UkwClearHaltDevice(priv->dev, endpoint)) {
        return translate_driver_error(GetLastError());
    }
    return LIBUSB_SUCCESS;
}

static int wince_reset_device(
    struct libusb_device_handle *handle)
{
    struct wince_device_priv *priv = _device_priv(handle->dev);
    if (!UkwResetDevice(priv->dev)) {
        return translate_driver_error(GetLastError());
    }
    return LIBUSB_SUCCESS;
}

static int wince_kernel_driver_active(
    struct libusb_device_handle *handle,
    int interface_number)
{
    struct wince_device_priv *priv = _device_priv(handle->dev);
    BOOL result = FALSE;
    if (!UkwKernelDriverActive(priv->dev, interface_number, &result)) {
        return translate_driver_error(GetLastError());
    }
    return result ? 1 : 0;
}

static int wince_detach_kernel_driver(
    struct libusb_device_handle *handle,
    int interface_number)
{
    struct wince_device_priv *priv = _device_priv(handle->dev);
    if (!UkwDetachKernelDriver(priv->dev, interface_number)) {
        return translate_driver_error(GetLastError());
    }
    return LIBUSB_SUCCESS;
}

static int wince_attach_kernel_driver(
    struct libusb_device_handle *handle,
    int interface_number)
{
    struct wince_device_priv *priv = _device_priv(handle->dev);
    if (!UkwAttachKernelDriver(priv->dev, interface_number)) {
        return translate_driver_error(GetLastError());
    }
    return LIBUSB_SUCCESS;
}

static void wince_destroy_device(
    struct libusb_device *dev)
{
    struct wince_device_priv *priv = _device_priv(dev);
    UkwReleaseDeviceList(driver_handle, &priv->dev, 1);
}

static void wince_clear_transfer_priv(
    struct usbi_transfer *itransfer)
{
    struct wince_transfer_priv *transfer_priv = (struct wince_transfer_priv*)usbi_transfer_get_os_priv(itransfer);
    struct winfd wfd = fd_to_winfd(transfer_priv->pollable_fd.fd);
    // No need to cancel transfer as it is either complete or abandoned
    wfd.itransfer = NULL;
    CloseHandle(wfd.handle);
    usbi_free_fd(&transfer_priv->pollable_fd);
}

static int wince_cancel_transfer(
    struct usbi_transfer *itransfer)
{
    struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
    struct wince_device_priv *priv = _device_priv(transfer->dev_handle->dev);
    struct wince_transfer_priv *transfer_priv = (struct wince_transfer_priv*)usbi_transfer_get_os_priv(itransfer);

    if (!UkwCancelTransfer(priv->dev, transfer_priv->pollable_fd.overlapped, UKW_TF_NO_WAIT)) {
        return translate_driver_error(GetLastError());
    }
    return LIBUSB_SUCCESS;
}

static int wince_submit_control_or_bulk_transfer(struct usbi_transfer *itransfer)
{
    struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
    struct libusb_context *ctx = DEVICE_CTX(transfer->dev_handle->dev);
    struct wince_transfer_priv *transfer_priv = (struct wince_transfer_priv*)usbi_transfer_get_os_priv(itransfer);
    struct wince_device_priv *priv = _device_priv(transfer->dev_handle->dev);
    BOOL direction_in, ret;
    struct winfd wfd;
    DWORD flags;
    HANDLE eventHandle;
    PUKW_CONTROL_HEADER setup = NULL;
    const BOOL control_transfer = transfer->type == LIBUSB_TRANSFER_TYPE_CONTROL;

    transfer_priv->pollable_fd = INVALID_WINFD;
    if (control_transfer) {
        setup = (PUKW_CONTROL_HEADER) transfer->buffer;
        direction_in = setup->bmRequestType & LIBUSB_ENDPOINT_IN;
    } else {
        direction_in = transfer->endpoint & LIBUSB_ENDPOINT_IN;
    }
    flags = direction_in ? UKW_TF_IN_TRANSFER : UKW_TF_OUT_TRANSFER;
    flags |= UKW_TF_SHORT_TRANSFER_OK;

    eventHandle = CreateEvent(NULL, FALSE, FALSE, NULL);
    if (eventHandle == NULL) {
        usbi_err(ctx, "Failed to create event for async transfer");
        return LIBUSB_ERROR_NO_MEM;
    }

    wfd = usbi_create_fd(eventHandle, direction_in ? RW_READ : RW_WRITE, itransfer, &wince_cancel_transfer);
    if (wfd.fd < 0) {
        CloseHandle(eventHandle);
        return LIBUSB_ERROR_NO_MEM;
    }

    transfer_priv->pollable_fd = wfd;
    if (control_transfer) {
        // Split out control setup header and data buffer
        DWORD bufLen = transfer->length - sizeof(UKW_CONTROL_HEADER);
        PVOID buf = (PVOID) &transfer->buffer[sizeof(UKW_CONTROL_HEADER)];

        ret = UkwIssueControlTransfer(priv->dev, flags, setup, buf, bufLen, &transfer->actual_length, wfd.overlapped);
    } else {
        ret = UkwIssueBulkTransfer(priv->dev, flags, transfer->endpoint, transfer->buffer,
            transfer->length, &transfer->actual_length, wfd.overlapped);
    }
    if (!ret) {
        int libusbErr = translate_driver_error(GetLastError());
        usbi_err(ctx, "UkwIssue%sTransfer failed: error %d",
            control_transfer ? "Control" : "Bulk", GetLastError());
        wince_clear_transfer_priv(itransfer);
        return libusbErr;
    }
    usbi_add_pollfd(ctx, transfer_priv->pollable_fd.fd, direction_in ? POLLIN : POLLOUT);
    itransfer->flags |= USBI_TRANSFER_UPDATED_FDS;

    return LIBUSB_SUCCESS;
}

static int wince_submit_iso_transfer(struct usbi_transfer *itransfer)
{
    return LIBUSB_ERROR_NOT_SUPPORTED;
}

static int wince_submit_transfer(
    struct usbi_transfer *itransfer)
{
    struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);

    switch (transfer->type) {
    case LIBUSB_TRANSFER_TYPE_CONTROL:
    case LIBUSB_TRANSFER_TYPE_BULK:
    case LIBUSB_TRANSFER_TYPE_INTERRUPT:
        return wince_submit_control_or_bulk_transfer(itransfer);
    case LIBUSB_TRANSFER_TYPE_ISOCHRONOUS:
        return wince_submit_iso_transfer(itransfer);
    default:
        usbi_err(TRANSFER_CTX(transfer), "unknown endpoint type %d", transfer->type);
        return LIBUSB_ERROR_INVALID_PARAM;
    }
}

static void wince_transfer_callback(struct usbi_transfer *itransfer, uint32_t io_result, uint32_t io_size)
{
    struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
    struct wince_transfer_priv *transfer_priv = (struct wince_transfer_priv*)usbi_transfer_get_os_priv(itransfer);
    struct wince_device_priv *priv = _device_priv(transfer->dev_handle->dev);
    int status;

    usbi_dbg("handling I/O completion with errcode %d", io_result);

    if (io_result == ERROR_NOT_SUPPORTED &&
        transfer->type != LIBUSB_TRANSFER_TYPE_CONTROL) {
        /* For functional stalls, the WinCE USB layer (and therefore the USB Kernel Wrapper
         * Driver) will report USB_ERROR_STALL/ERROR_NOT_SUPPORTED in situations where the
         * endpoint isn't actually stalled.
         *
         * One example of this is that some devices will occasionally fail to reply to an IN
         * token. The WinCE USB layer carries on with the transaction until it is completed
         * (or cancelled) but then completes it with USB_ERROR_STALL.
         *
         * This code therefore needs to confirm that there really is a stall error, by both
         * checking the pipe status and requesting the endpoint status from the device.
         */
        BOOL halted = FALSE;
        usbi_dbg("checking I/O completion with errcode ERROR_NOT_SUPPORTED is really a stall");
        if (UkwIsPipeHalted(priv->dev, transfer->endpoint, &halted)) {
            /* Pipe status retrieved, so now request endpoint status by sending a GET_STATUS
             * control request to the device. This is done synchronously, which is a bit
             * naughty, but this is a special corner case.
             */
            WORD wStatus = 0;
            DWORD written = 0;
            UKW_CONTROL_HEADER ctrlHeader;
            ctrlHeader.bmRequestType = LIBUSB_REQUEST_TYPE_STANDARD |
                LIBUSB_ENDPOINT_IN | LIBUSB_RECIPIENT_ENDPOINT;
            ctrlHeader.bRequest = LIBUSB_REQUEST_GET_STATUS;
            ctrlHeader.wValue = 0;
            ctrlHeader.wIndex = transfer->endpoint;
            ctrlHeader.wLength = sizeof(wStatus);
            if (UkwIssueControlTransfer(priv->dev,
                    UKW_TF_IN_TRANSFER | UKW_TF_SEND_TO_ENDPOINT,
                    &ctrlHeader, &wStatus, sizeof(wStatus), &written, NULL)) {
                if (written == sizeof(wStatus) &&
                        (wStatus & STATUS_HALT_FLAG) == 0) {
                    if (!halted || UkwClearHaltHost(priv->dev, transfer->endpoint)) {
                        usbi_dbg("Endpoint doesn't appear to be stalled, overriding error with success");
                        io_result = ERROR_SUCCESS;
                    } else {
                        usbi_dbg("Endpoint doesn't appear to be stalled, but the host is halted, changing error");
                        io_result = ERROR_IO_DEVICE;
                    }
                }
            }
        }
    }

    switch(io_result) {
    case ERROR_SUCCESS:
        itransfer->transferred += io_size;
        status = LIBUSB_TRANSFER_COMPLETED;
        break;
    case ERROR_CANCELLED:
        usbi_dbg("detected transfer cancel");
        status = LIBUSB_TRANSFER_CANCELLED;
        break;
    case ERROR_NOT_SUPPORTED:
    case ERROR_GEN_FAILURE:
        usbi_dbg("detected endpoint stall");
        status = LIBUSB_TRANSFER_STALL;
        break;
    case ERROR_SEM_TIMEOUT:
        usbi_dbg("detected semaphore timeout");
        status = LIBUSB_TRANSFER_TIMED_OUT;
        break;
    case ERROR_OPERATION_ABORTED:
        if (itransfer->flags & USBI_TRANSFER_TIMED_OUT) {
            usbi_dbg("detected timeout");
            status = LIBUSB_TRANSFER_TIMED_OUT;
        } else {
            usbi_dbg("detected operation aborted");
            status = LIBUSB_TRANSFER_CANCELLED;
        }
        break;
    default:
        usbi_err(ITRANSFER_CTX(itransfer), "detected I/O error: %s", windows_error_str(io_result));
        status = LIBUSB_TRANSFER_ERROR;
        break;
    }
    wince_clear_transfer_priv(itransfer);
    if (status == LIBUSB_TRANSFER_CANCELLED) {
        usbi_handle_transfer_cancellation(itransfer);
    } else {
        usbi_handle_transfer_completion(itransfer, (enum libusb_transfer_status)status);
    }
}

static void wince_handle_callback (struct usbi_transfer *itransfer, uint32_t io_result, uint32_t io_size)
{
    struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);

    switch (transfer->type) {
    case LIBUSB_TRANSFER_TYPE_CONTROL:
    case LIBUSB_TRANSFER_TYPE_BULK:
    case LIBUSB_TRANSFER_TYPE_INTERRUPT:
    case LIBUSB_TRANSFER_TYPE_ISOCHRONOUS:
        wince_transfer_callback (itransfer, io_result, io_size);
        break;
    default:
        usbi_err(ITRANSFER_CTX(itransfer), "unknown endpoint type %d", transfer->type);
    }
}

static int wince_handle_events(
    struct libusb_context *ctx,
    struct pollfd *fds, POLL_NFDS_TYPE nfds, int num_ready)
{
    struct wince_transfer_priv* transfer_priv = NULL;
    POLL_NFDS_TYPE i = 0;
    BOOL found = FALSE;
    struct usbi_transfer *transfer;
    DWORD io_size, io_result;

    usbi_mutex_lock(&ctx->open_devs_lock);
    for (i = 0; i < nfds && num_ready > 0; i++) {

        usbi_dbg("checking fd %d with revents = %04x", fds[i].fd, fds[i].revents);

        if (!fds[i].revents) {
            continue;
        }

        num_ready--;

        // Because a Windows OVERLAPPED is used for poll emulation,
        // a pollable fd is created and stored with each transfer
        usbi_mutex_lock(&ctx->flying_transfers_lock);
        list_for_each_entry(transfer, &ctx->flying_transfers, list, struct usbi_transfer) {
            transfer_priv = usbi_transfer_get_os_priv(transfer);
            if (transfer_priv->pollable_fd.fd == fds[i].fd) {
                found = TRUE;
                break;
            }
        }
        usbi_mutex_unlock(&ctx->flying_transfers_lock);

        if (found && HasOverlappedIoCompleted(transfer_priv->pollable_fd.overlapped)) {
            io_result = (DWORD)transfer_priv->pollable_fd.overlapped->Internal;
            io_size = (DWORD)transfer_priv->pollable_fd.overlapped->InternalHigh;
            usbi_remove_pollfd(ctx, transfer_priv->pollable_fd.fd);
            // let handle_callback free the event using the transfer wfd
            // If you don't use the transfer wfd, you run a risk of trying to free a
            // newly allocated wfd that took the place of the one from the transfer.
            wince_handle_callback(transfer, io_result, io_size);
        } else if (found) {
            usbi_err(ctx, "matching transfer for fd %x has not completed", fds[i]);
            return LIBUSB_ERROR_OTHER;
        } else {
            usbi_err(ctx, "could not find a matching transfer for fd %x", fds[i]);
            return LIBUSB_ERROR_NOT_FOUND;
        }
    }

    usbi_mutex_unlock(&ctx->open_devs_lock);
    return LIBUSB_SUCCESS;
}

/*
 * Monotonic and real time functions
 */
unsigned __stdcall wince_clock_gettime_threaded(void* param)
{
    LARGE_INTEGER hires_counter, li_frequency;
    LONG nb_responses;
    int timer_index;

    // Init - find out if we have access to a monotonic (hires) timer
    if (!QueryPerformanceFrequency(&li_frequency)) {
        usbi_dbg("no hires timer available on this platform");
        hires_frequency = 0;
        hires_ticks_to_ps = UINT64_C(0);
    } else {
        hires_frequency = li_frequency.QuadPart;
        // The hires frequency can go as high as 4 GHz, so we'll use a conversion
        // to picoseconds to compute the tv_nsecs part in clock_gettime
        hires_ticks_to_ps = UINT64_C(1000000000000) / hires_frequency;
        usbi_dbg("hires timer available (Frequency: %"PRIu64" Hz)", hires_frequency);
    }

    // Signal wince_init() that we're ready to service requests
    if (ReleaseSemaphore(timer_response, 1, NULL) == 0) {
        usbi_dbg("unable to release timer semaphore: %s", windows_error_str(0));
    }

    // Main loop - wait for requests
    while (1) {
        timer_index = WaitForMultipleObjects(2, timer_request, FALSE, INFINITE) - WAIT_OBJECT_0;
        if ( (timer_index != 0) && (timer_index != 1) ) {
            usbi_dbg("failure to wait on requests: %s", windows_error_str(0));
            continue;
        }
        if (request_count[timer_index] == 0) {
            // Request already handled
            ResetEvent(timer_request[timer_index]);
            // There's still a possiblity that a thread sends a request between the
            // time we test request_count[] == 0 and we reset the event, in which case
            // the request would be ignored. The simple solution to that is to test
            // request_count again and process requests if non zero.
            if (request_count[timer_index] == 0)
                continue;
        }
        switch (timer_index) {
        case 0:
            WaitForSingleObject(timer_mutex, INFINITE);
            // Requests to this thread are for hires always
            if (QueryPerformanceCounter(&hires_counter) != 0) {
                timer_tp.tv_sec = (long)(hires_counter.QuadPart / hires_frequency);
                timer_tp.tv_nsec = (long)(((hires_counter.QuadPart % hires_frequency)/1000) * hires_ticks_to_ps);
            } else {
                // Fallback to real-time if we can't get monotonic value
                // Note that real-time clock does not wait on the mutex or this thread.
                wince_clock_gettime(USBI_CLOCK_REALTIME, &timer_tp);
            }
            ReleaseMutex(timer_mutex);

            nb_responses = InterlockedExchange((LONG*)&request_count[0], 0);
            if ( (nb_responses)
              && (ReleaseSemaphore(timer_response, nb_responses, NULL) == 0) ) {
                usbi_dbg("unable to release timer semaphore: %s", windows_error_str(0));
            }
            continue;
        case 1: // time to quit
            usbi_dbg("timer thread quitting");
            return 0;
        }
    }
    usbi_dbg("ERROR: broken timer thread");
    return 1;
}

static int wince_clock_gettime(int clk_id, struct timespec *tp)
{
    FILETIME filetime;
    ULARGE_INTEGER rtime;
    DWORD r;
    SYSTEMTIME st;
    switch(clk_id) {
    case USBI_CLOCK_MONOTONIC:
        if (hires_frequency != 0) {
            while (1) {
                InterlockedIncrement((LONG*)&request_count[0]);
                SetEvent(timer_request[0]);
                r = WaitForSingleObject(timer_response, TIMER_REQUEST_RETRY_MS);
                switch(r) {
                case WAIT_OBJECT_0:
                    WaitForSingleObject(timer_mutex, INFINITE);
                    *tp = timer_tp;
                    ReleaseMutex(timer_mutex);
                    return LIBUSB_SUCCESS;
                case WAIT_TIMEOUT:
                    usbi_dbg("could not obtain a timer value within reasonable timeframe - too much load?");
                    break; // Retry until successful
                default:
                    usbi_dbg("WaitForSingleObject failed: %s", windows_error_str(0));
                    return LIBUSB_ERROR_OTHER;
                }
            }
        }
        // Fall through and return real-time if monotonic was not detected @ timer init
    case USBI_CLOCK_REALTIME:
        // We follow http://msdn.microsoft.com/en-us/library/ms724928%28VS.85%29.aspx
        // with a predef epoch_time to have an epoch that starts at 1970.01.01 00:00
        // Note however that our resolution is bounded by the Windows system time
        // functions and is at best of the order of 1 ms (or, usually, worse)
        GetSystemTime(&st);
        SystemTimeToFileTime(&st, &filetime);
        rtime.LowPart = filetime.dwLowDateTime;
        rtime.HighPart = filetime.dwHighDateTime;
        rtime.QuadPart -= epoch_time;
        tp->tv_sec = (long)(rtime.QuadPart / 10000000);
        tp->tv_nsec = (long)((rtime.QuadPart % 10000000)*100);
        return LIBUSB_SUCCESS;
    default:
        return LIBUSB_ERROR_INVALID_PARAM;
    }
}

const struct usbi_os_backend wince_backend = {
        "Windows CE",
        0,
        wince_init,
        wince_exit,

        wince_get_device_list,
    NULL,                /* hotplug_poll */
        wince_open,
        wince_close,

        wince_get_device_descriptor,
        wince_get_active_config_descriptor,
        wince_get_config_descriptor,
    NULL,                /* get_config_descriptor_by_value() */

        wince_get_configuration,
        wince_set_configuration,
        wince_claim_interface,
        wince_release_interface,

        wince_set_interface_altsetting,
        wince_clear_halt,
        wince_reset_device,

        wince_kernel_driver_active,
        wince_detach_kernel_driver,
        wince_attach_kernel_driver,

        wince_destroy_device,

        wince_submit_transfer,
        wince_cancel_transfer,
        wince_clear_transfer_priv,

        wince_handle_events,

        wince_clock_gettime,
        sizeof(struct wince_device_priv),
        sizeof(struct wince_device_handle_priv),
        sizeof(struct wince_transfer_priv),
        0,
};

